.TH std::is_lvalue_reference 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::is_lvalue_reference \- std::is_lvalue_reference

.SH Synopsis
   Defined in header <type_traits>
   template< class T >              \fI(since C++11)\fP
   struct is_lvalue_reference;

   std::is_lvalue_reference is a UnaryTypeTrait.

   Checks whether T is an lvalue reference type. Provides the member constant value
   which is equal to true, if T is an lvalue reference type. Otherwise, value is equal
   to false.

   If the program adds specializations for std::is_lvalue_reference or
   std::is_lvalue_reference_v, the behavior is undefined.

.SH Template parameters

   T - a type to check

   Helper variable template

   template< class T >
   inline constexpr bool is_lvalue_reference_v =                          \fI(since C++17)\fP
   is_lvalue_reference<T>::value;



Inherited from std::integral_constant

.SH Member constants

   value    true if T is an lvalue reference type, false otherwise
   \fB[static]\fP \fI(public static member constant)\fP

.SH Member functions

   operator bool converts the object to bool, returns value
                 \fI(public member function)\fP
   operator()    returns value
   \fI(C++14)\fP       \fI(public member function)\fP

.SH Member types

   Type       Definition
   value_type bool
   type       std::integral_constant<bool, value>

.SH Possible implementation

   template<class T> struct is_lvalue_reference     : std::false_type {};
   template<class T> struct is_lvalue_reference<T&> : std::true_type {};

.SH Example


// Run this code

 #include <iostream>
 #include <type_traits>

 class A {};

 int main()
 {
     std::cout << std::boolalpha;
     std::cout << std::is_lvalue_reference<A>::value << '\\n';
     std::cout << std::is_lvalue_reference<A&>::value << '\\n';
     std::cout << std::is_lvalue_reference<A&&>::value << '\\n';
     std::cout << std::is_lvalue_reference<int>::value << '\\n';
     std::cout << std::is_lvalue_reference<int&>::value << '\\n';
     std::cout << std::is_lvalue_reference<int&&>::value << '\\n';
 }

.SH Output:

 false
 true
 false
 false
 true
 false

.SH See also

   is_reference        checks if a type is either an lvalue reference or rvalue
   \fI(C++11)\fP             reference
                       \fI(class template)\fP
   is_rvalue_reference checks if a type is an rvalue reference
   \fI(C++11)\fP             \fI(class template)\fP
